504 ANNUAL REPORT SMITHSONIAN INSTITUTION^ 1915. 



velopments of electrical science. For this reason it will doubtless 

 suffice to confine our consideration to what has been done during the 

 last five years. 



At the beginning of the present decade:, radiotelegraphy, although 

 serving a useful purpose in connection with ship-to-ship and ship-to- 

 shore services, was still in a very unsatisfactory condition. Very 

 little had as yet been done in the matter of developing successful 

 long-distance communication. With one or two minor exceptions of 

 what were in reality experimental installations, practically all radio- 

 communication was on a spark-system basis. Continuous wave train 

 systems were beginning to loom up as possibilities of the future, and 

 controversies as to the relative merits of such systems and the already 

 known spark systems had already begun. 



At the time in question — say, 1900 — radiotelephony, except as a 

 theoretical possibility supported by a few rather unsatisfactory 

 demonstrations of an experimental character, did not exist. Certain 

 things had, however, been reasonably well determined as essential to 

 any future development along this line; for example, the necessity 

 for a continuous or almost continuous form of wave train and some- 

 thing other than the direct insertion of a telephone transmitter in 

 the antenna circuit for modifying the high-frequency waves. 



By the first of 1913 what was termed commercial trans-Atlantic 

 communication by radiotelegraphy had been ajccomplished, and 

 although spark sj^stems were still in the gi-eat majority, continuous- 

 oscillation systems were beginning to come into favor, particularly 

 for long-distance service. In a practical sense, radiotelephony had 

 not, however, made very much progress. 



GENERATING APPARATUS. 



During the past five years most of the progress in the field of gen- 

 erating apparatus has been in the direction of producing continuous 

 oscillations of large power. In this connection should be mentioned 

 the Goldschmidt generator, the static frequency changers of the 

 Telefunken Co., improvements in the Poulsen arc intended to give a 

 larger out^Dut and more stable operation, the high frequency alter- 

 nators developed by the General Electric Co., and thermionic de- 

 vices. Some of this apparatus has reached the stage where it is in 

 everyday commercial service, while the rest is still largely in the 

 experimental stage. 



RADIATING SYSTEMS. 



During the past few years practically nothing of importance has 

 been published on the fundamental principles of radiating systems. 

 The general trend of commercial or experimental radio station con- 



